The present invention relates to the measurement of electrical impedances and, in particular, to the measurement of the impedance of very reactive loads.
It is generally difficult to measure the impedance of very reactive loads because the value changes so rapidly with respect to frequency.
For example, solar cells may appear so capacitive that nearly any voltage applied by a test instrument will want to oscillate into the cell's highly reactive load. Making matters worse, the noise in the test voltage will also result in corresponding large noise currents in the low impedance of the cell. Batteries and “super” capacitors also have these issues.
A similar circumstance can occur, for example, in high efficiency motors, such as some rare-earth permanent magnet motors which may appear so inductive that nearly any current applied by a test instrument will produce analogous results.